1. Field of the Invention
The present invention relates to a blower designed to suppress noise.
2. Description of the Related Art
A conventional blower is described below with reference to FIGS. 6 and 7. In each of the figures, reference numeral 1 designates a casing comprising a main body 1a and a cover 1b, which is formed to have inlet ports 1c and an outlet port 1d for air. A motor 2 and an impeller 3 are housed within the casing 1. The impeller 3 is rotated by the motor 2 in the direction of an arrow A in FIG. 6. By the rotation of the impeller 3, air is sucked from the inlet ports 1c of the casing 1 as shown by an arrow B in FIG. 7, and is discharged from the outlet port 1d as shown by an arrow C in FIG. 6 to send air.
Since air is sent in accordance with the rotation of the impeller 3, the wind thereby created forms a current (air flow) which flows slightly in the rotating direction of the impeller 3. Referring to the conventional blower described above, a wind-receiving end 1d1 of the outlet port 1d located on the inward side of an air flow (the lower side in the drawing) is formed in parallel with sides (long sides) 3a1 extending along the direction (horizontal direction) of the rotation axis of a vane 3a (as illustrated in FIG. 7).
Therefore, the wind sent and blown out by the vanes 3a of the impeller 3 blows against the wind-receiving end 1d1 of the outlet port 1d all at once throughout its entire width, which causes a loud wind noise. More specifically, the result of the measurement shown in FIG. 8 (the result gained at a distance of 1 m away from the outlet port 1d) reveals that a noticeable peak tone 81 is generated in the vicinity of the frequency of 3 kHz. As this peak tone is often sensed as a harsh noise, it was a demand to overcome this problem.